This invention relates in general to body and frame assemblies for vehicles. More specifically, this invention relates to an improved method for manufacturing an engine cradle for use with such a vehicular body and frame assembly.
Virtually all land vehicles in common use, such as automobiles, vans, and trucks, include a body and frame assembly which is supported upon a plurality of ground-engaging wheels by a resilient suspension system. The structures of known body and frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate body and frame assembly, the structural components of the body portion and the frame portion are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate body and frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modem vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized body and frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit which is resiliently supported upon the vehicle wheels by the suspension system. Unitized body and frame assemblies of this general type are found in many relatively small modern vehicles, such as automobiles and minivans.
In both types of body and frame assemblies, it is known to provide a specialized structure for supporting the engine of the vehicle thereon. This engine support structure, which is commonly referred to as an engine cradle, is frequently embodied as a generally U-shaped member having a central portion and a pair of leg portions. Engine mount portions and body mount portions are formed at various locations on the engine cradle. The engine mount portions are provided for facilitating the connection of the engine to the engine cradle, while the body mount portions are provided for facilitating the connection of the engine cradle to the body and frame assembly. Usually, bolts or similar fasteners are used to provide the various connections between the engine, the engine cradle, and the body and frame assembly. Thus, the engine cradle securely supports the engine on the body and frame assembly of the vehicle during use.
In the past, engine cradles were usually formed by stamping a number of flat metallic components into desired configurations and securing the stamped components together, such as by welding. Engine cradles of this general type have been found to be effective, but are relatively time consuming and expensive to manufacture because they involve the manufacture and handling of a relatively large number of individual components. More recently, engine cradles have been formed from a single tubular member using the process of hydroforming. Hydroforming is an advantageous process for forming engine cradles and other structures because it can quickly deform a single component into a desired shape. To accomplish this, the tubular member was initially pre-bent in a tube bending apparatus to a desired preliminary shape. Then, the pre-bent tube was disposed between two die sections of a hydroforming apparatus which, when closed together, defined a die cavity having a desired final shape. Thereafter, the tubular member was filled with a pressurized fluid, typically a relatively incompressible liquid such as water. The pressure of the fluid was increased to a magnitude where the tubular member was deformed into conformance with the die cavity and, thus, the desired final shape.
Although hydroforming has been found to be effective to reduce manufacturing time and complexity by minimizing the number of components and eliminating the securement of the various components together, it has the inherent drawback that only a single piece of material can be used to form the engine cradle. Thus, the size, shape, and composition of the piece of material must be selected to satisfy all of the design requirements throughout the entire engine cradle. As a result, one or more locations of the hydroformed engine cradle may be formed having a size, shape, or composition that exceeds the design requirements at those locations. This can result in undesirable addition of weight or cost to the overall engine cradle. Thus, it would be desirable to provide an improved method for manufacturing an engine cradle that incorporates the advantages of hydroforming, while allowing the use of alternative materials to form different portions of the engine cradle.
This invention relates to an improved method for manufacturing an engine cradle for use with a vehicular body and frame assembly. Initially, desired materials are selected for each of four hollow members that will be secured together to form the engine cradle. The selected materials can include metallic materials, such as steel, aluminum, magnesium, and non-metallic materials, such as fiber and other composites, or any combination thereof The selected materials are formed into desired shapes using any known method, such as by hydroforming. Then, portions of the four members are disposed in a telescoping relationship with one another, such as by providing protrusions on some of the components and disposing the ends of the other components in a telescoping relationship with such protrusions. Lastly, the telescoping portions of the members are secured together using any securement 9 method, including laser, MIG, or electromagnetic pulse welding techniques and adhesive bonding.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.